The invention is in the field of electronic circuits for operating high-pressure, high-intensity arc lamps. An example of one of many such type lamps is disclosed in U.S. Pat. No. 3,305,289 to Elmer Fridrich. Such lamps operate in three modes:
(1) Starting mode (comprising a glow breakdown mode followed by a glow-to-arc transition) in which a relatively high value of a-c or d-c starting voltage is applied across the lamp's electrodes to first condition the lamp's gases into a suitable ionized condition for striking a glow, followed by a time period up to a minute or so to cause a transition into an arc between the lamp's electrode tips;
(2) Operating mode, in which the lamp's arc discharge generates desired light output and a relatively low or moderate voltage occurs across the lamp's electrodes in response to a suitable arc discharge current as established by the ballast circuit; and
(3) Hot Restart mode, in which the lamp's arc discharge fails or extinguishes for some reason such as a momentary interruption of its current supply. If the arc extinguishes, the lamp must be permitted to cool for up to a minute or more before the arc can be restarted by the normal starting voltage.
In contrast to the foregoing, low-pressure lamps such as fluorescent lamps can be started with a single short-duration relatively low voltage pulse, and furthermore do not have a hot restart problem.
Numerous circuits have been devised for starting, operating, and hot-restarting high-pressure arc lamps. Some examples are disclosed in U.S. Pat. No. 4,060,751 to Thomas E. Anderson, which discloses a variable frequency L-C resonant starting inverter circuit which increases the starting voltage until the arc is established in the lamp and the inverter circuit then functions as the operating ballast; and in U.S. Pat. No. 4,048,539 to Walker and Kornrumpf which discloses a circuit having a starting transformer secondary in series with the arc lamp to provide starting and hot-restarting of the lamp.